The present invention relates generally to the field of communication systems. More specifically, embodiments of the invention relate to a system for communicating high-speed signals between multiple printed circuit boards (PCBs).
A PCB is found in almost every electronic device. Electronic components and integrated circuits (ICs) in a device are mounted on the PCB. A network of wires provides the electrical connections between the electronic components mounted on the PCB. These wires are referred to as ‘traces’.
The most basic PCBs have the electronic components mounted on one side of the board and the traces on the opposite side. These PCBs are called single-sided PCBs. However, these PCBs have several limitations when it comes to routing the traces. This is because the conducting traces are present only on one side and they cannot cross each other. Therefore, the single-sided PCBs have been replaced by double-sided PCBs, which have traces on both sides of the board. The double-sided PCBs overcome most of the limitations of the single-sided PCBs. Thus, double-sided PCBs are more suited for complex circuits. To further increase the area available for wiring, multi-layer PCBs are used which have one or more traces inside the board. The total number of layers in multi-layer PCBs is usually an even number. The total number of layers includes the two outer layers. Most multi-layer PCBs have a total of four to eight layers.
Modern communication systems are increasingly dependent on high-speed signaling. Complicated PCB-based circuits are required to support higher communication speeds. These circuits, in turn, require greater packaging space. However, greater packaging space implies an unrealizable increase in the size of the communication equipment that comprise the packages. Accordingly, higher communication speeds have led to a need for packing the circuits in compact spaces. Thus, there is an increasing demand for greater miniaturization. Flexible circuits help in realizing this demand. Therefore, the need for improved fabrication methods for making flexible circuits is becoming more important. This has forced PCB designers to not only use multi-layer PCBs, but to modularize systems that have multiple PCBs. Presently, the signals travel between these multiple PCBs by way of jumpers, connectors and cable wires. However, jumpering between the PCBs with the cable wires or other connectors does not provide the performance that is required for communicating high-speed signals. A variety of fabrication and assembly techniques are used to attach the connectors to the multiple PCBs such as pins soldered into plates through holes, pins with compliant sections pressed into plates through holes, and surface mounted leads attached to pads on the surface of the PCB.
The above-mentioned techniques require additional processing efforts to attach the connectors to the PCBs. Separate connector components and processing efforts increase the cost of assembling the PCBs. In addition, such techniques require soldering different components together. However, soldering leads to reliability problems associated with the solder joints. Further, it is difficult to maintain uniform impedance between the multiple PCBs and the connectors using the above-mentioned techniques. The variation in the impedance leads to the problem of reflections. Reflections are unwanted signals that propagate on the signaling paths due to an impedance mismatch. As a result, it is difficult to maintain the integrity of high-speed signals that are communicated between the multiple PCBs. Furthermore, the jumpers, the connectors, and the cable wires used in the above-mentioned techniques are not flexible. As a result, it is difficult to pack the different components in a small volume.
Hence, there exists a need for a system and a method that preserves the integrity of high-speed signals between multiple PCBs. Also, there is a need for a system and a method for connecting different PCBs so that uniform impedance is maintained. In addition, there is a need for a system that is cost effective, reliable and less voluminous.